The present invention relates to an anodizing apparatus, an anodizing system, a substrate processing apparatus and method, and a substrate manufacturing method.
Porous silicon was found by A. Uhlir and D. R. Turner who were studying electropolishing of single-crystal silicon biased to a positive potential in an aqueous solution of hydrofluoric acid.
Later, to exploit excellent reactivity of porous silicon, application of porous silicon to the element isolation process in manufacturing a silicon integrated circuit was examined, and a full isolation technology (FIFOS: Full Isolation by Porous Oxidized Silicon) using a porous silicon oxide film was developed (K. Imai, Solid State Electron 24, 159, 1981).
Recently, an applied technology to direct bonding has been developed in which a silicon epitaxial layer is grown on a porous silicon substrate, and the substrate is bonded to an amorphous substrate or single-crystal silicon substrate via the oxide film (Japanese Patent Laid-Open No. 5-21338).
As another application example, porous silicon has received a great deal of attention as a photoluminescence or electroluminescence material that emits light by itself (Japanese Patent Laid-Open No. 6-338631).
A conventional anodizing apparatus for manufacturing a substrate having a porous silicon layer will be described below.
FIG. 20 is a view showing the arrangement of a conventional anodizing apparatus (Japanese Patent Laid-Open No. 60-94737). In this anodizing apparatus, anodizing tanks 1902a and 1902b made of Teflon (tradename of du Pont in the U.S.A) as a material with HF resistance are arranged to sandwich a silicon substrate 1901 from both sides. The anodizing tanks 1902a and 1902b respectively have O-rings 1904a and 1904b for sealing at portions where the silicon substrate 1901 is held. The anodizing tanks 1902a and 1902b have platinum electrodes 1903a and 1903b, respectively. After the silicon substrate 1901 is sandwiched by the two anodizing tanks 1902a and 1902b, the anodizing tanks 1902a and 1902b are filled with HF solutions 1905a and 1905b, respectively. In this state, a DC voltage is applied between the electrodes by setting the platinum electrode 1903a as a negative electrode and the platinum electrode 1903b as a positive electrode. The silicon substrate 1901 is anodized, and a porous silicon layer is formed on the negative-electrode-side surface of the silicon substrate 1901.
In such conventional scheme of vertically holding a silicon substrate and anodizing it, a gas (e.g., hydrogen gas) generated by the anodizing reaction may stay on the surface of the silicon substrate for a long time or rise along the surface of the silicon substrate. In this case, the track of gas remains on the surface of the porous layer formed on the silicon substrate. This makes the porous layer nonuniform to result in poor quality and a decrease in yield and productivity. Hence, a demand has arisen for introduction of a new scheme of preventing a gas generated by the anodizing reaction from adversely affecting anodizing.
To obtain high quality and productivity for substrates having a porous silicon layer, it is important to reduce contamination of a silicon substrate during anodizing, and reduce contamination of a silicon substrate during a series of processes including anodizing and associated processes (e.g., washing and drying).
To increase productivity of substrates having a porous silicon layer, it is also important to increase the speed of the series of processes including anodizing and associated processes.
Additionally, in consideration of the recent tendency of an increase in diameter of silicon substrates, it is also important to propose a scheme capable of easily coping with the increase in diameter.
The present invention has been made in consideration of the above situation, and has as its object to provide a new anodizing scheme.
More specifically, it is an object of the present invention to, e.g., prevent any influence of a gas generated by an anodizing reaction.
It is another object of the present invention to, e.g., prevent any contamination of a substrate to be processed.
It is still another object of the present invention to, e.g., increase the speed of a series of processes including anodizing and associated processes.
It is still another object of the present invention to, e.g., facilitate to cope with an increase in diameter.
According to the first aspect of the present invention, there is provided an anodizing apparatus for anodizing a substrate, characterized by comprising a holding portion for substantially horizontally holding the substrate to be processed, a negative electrode arranged above the substrate to oppose the substrate, a positive electrode arranged under the substrate, and an anodizing tank for filling a space between the substrate and the negative electrode with an electrolyte, wherein the negative electrode has a function of preventing a gas from staying on a lower side.
In the anodizing apparatus according to the first aspect of the present invention, for example, the negative electrode preferably has a degassing hole for preventing the gas from staying on the lower side.
In the anodizing apparatus according to the first aspect of the present invention, for example, the positive electrode preferably supplies a current to the substrate to be processed while being in direct contact with a lower surface of the substrate in anodizing.
In the anodizing apparatus according to the first aspect of the present invention, for example, of the positive electrode, at least a portion which comes into contact with the substrate to be processed is preferably formed from a semiconductor material.
Preferably, the anodizing apparatus according to the first aspect of the present invention further comprises, e.g., an electrode support portion supporting the positive electrode, and the electrode support portion has a mechanism for attaching/detaching the positive electrode.
In the anodizing apparatus according to the first aspect of the present invention, for example, the positive electrode preferably has a chuck mechanism for chucking the substrate to be processed.
In the anodizing apparatus according to the first aspect of the present invention, for example, the chuck mechanism preferably comprises a vacuum chuck mechanism.
In the anodizing apparatus according to the first aspect of the present invention, for example, the holding portion preferably holds a peripheral portion of the lower surface of the substrate to be processed.
In the anodizing apparatus according to the first aspect of the present invention, for example, the holding portion preferably has a chuck portion for holding the substrate to be processed by chucking a peripheral portion of the lower surface of the substrate.
In the anodizing apparatus according to the first aspect of the present invention, for example, the anodizing tank preferably has an opening portion at a bottom portion and can be filled with a liquid when the holding portion holds the substrate to be processed.
In the anodizing apparatus according to the first aspect of the present invention, for example, the positive electrode preferably comes into contact with the lower surface of the substrate to be processed, inside the opening portion.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., an electrode elevating mechanism for vertically moving the positive electrode.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a rotary driving mechanism for rotating the substrate to be processed substantially in a horizontal plane to remove the liquid sticking to the substrate.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a rotary driving mechanism for, after the substrate is released from the holding portion, rotating the positive electrode chucking the substrate substantially in a horizontal plane to rotate the substrate.
Preferably, in the anodizing apparatus according to the first aspect of the present invention, for example, the anodizing tank has, at a bottom portion, an opening portion for bringing the positive electrode into contact with the lower surface of the substrate to be processed, and the holding portion is arranged in an annular shape along the opening portion at the bottom portion of the anodizing tank and holds the peripheral portion of the lower surface of the substrate to be processed.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., an electrode elevating mechanism for vertically moving the positive electrode, and a rotary driving mechanism for, after the electrode elevating mechanism moves the substrate to be processed upward to a position where the substrate is not in contact with the holding portion, rotating the positive electrode chucking the substrate substantially in a horizontal plane to rotate the substrate.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a substrate manipulation mechanism for receiving the substrate to be processed from a conveyor robot and causing the holding portion to hold the substrate.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a substrate manipulation mechanism for receiving the substrate to be processed from a conveyor robot, causing the holding portion to hold the substrate, and transferring the processed substrate to the conveyor robot or another conveyor robot.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., an elevating mechanism for receiving the substrate to be processed from a conveyor robot at an upper portion of the anodizing tank, moving the substrate downward, and causing the holding portion to hold the substrate.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a substrate elevating mechanism for receiving the substrate to be processed from a conveyor robot at an upper portion of the anodizing tank, moving the substrate downward, causing the holding portion to hold the substrate, receiving the processed substrate from the holding portion, moving the substrate upward, and transferring the substrate to the conveyor robot or another conveyor robot.
In the anodizing apparatus according to the first aspect of the present invention, for example, the elevating mechanism preferably has a support portion for supporting the substrate to be processed from the lower side and vertically moves the substrate placed on the support portion.
In the anodizing apparatus according to the first aspect of the present invention, for example, the support portion preferably receives/transfers the substrate to be processed from/to the conveyor robot in a substantially horizontal state.
In the anodizing apparatus according to the first aspect of the present invention, for example, the support portion preferably has a structure capable of receiving/transferring the substrate to be processed from/to the conveyor robot supporting the substrate from the lower side.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a driving mechanism for moving the negative electrode.
In the anodizing apparatus according to the first aspect of the present invention, for example, the driving mechanism preferably removes the negative electrode from the anodizing tank when the substrate to be processed is to be held by the holding portion, and makes the negative electrode oppose the substrate when the substrate is to be anodized.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a supply portion for supplying the electrolyte into the anodizing tank.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a discharge portion for discharging the electrolyte from the anodizing tank.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a circulation system for circulating the electrolyte while supplying the electrolyte into the anodizing tank and simultaneously discharging the electrolyte from the anodizing tank.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a supply portion for supplying a cleaning solution into the anodizing tank after the substrate is anodized.
The anodizing apparatus according to the first aspect of the present invention preferably further comprises, e.g., a discharge portion for discharging the cleaning solution from the anodizing tank.
The anodizing apparatus according to the first aspect of the present invention can preferably be used as, e.g., an apparatus for filling the anodizing tank with the electrolyte to anodize the substrate and then filling the anodizing tank with the cleaning solution to wash the substrate.
The anodizing apparatus according to the first aspect of the present invention can preferably be used as, e.g., an apparatus for filling the anodizing tank with the electrolyte to anodize the substrate, filling the anodizing tank with the cleaning solution to wash the substrate, and then drying the substrate.
According to the second aspect of the present invention, there is provided an anodizing apparatus for anodizing a substrate, characterized by comprising an anodizing tank, a negative electrode, a positive electrode, a first supply portion for supplying an electrolyte to a space between the negative electrode and the substrate using the anodizing tank to anodize the substrate by applying a voltage between the negative electrode and the positive electrode, and a second supply portion for supplying a cleaning solution to the substrate using the anodizing tank to wash the anodized substrate.
The anodizing apparatus according to the second aspect of the present invention preferably further comprises, e.g., a rotary driving mechanism for rotating the washed substrate in the anodizing tank to dry the substrate.
According to the third aspect of the present invention, there is provided a processing apparatus for a substrate, characterized by comprising a process tank and processing means for performing, for the substrate in the process tank, at least two consecutive processes of anodizing, washing, and drying.
In the substrate processing apparatus according to the third aspect of the present invention, for example, the processing means preferably processes the substrate while keeping the substrate in a substantially horizontal state.
In the substrate processing apparatus according to the third aspect of the present invention, for example, the processing means preferably processes the substrate while supporting the substrate.only from a lower side.
The substrate processing apparatus according to the third aspect of the present invention preferably further comprises, e.g., substrate manipulation means for receiving the substrate from a conveyor robot in a substantially horizontal state and processing the substrate, and transferring the processed substrate to the conveyor robot in the substantially horizontal state.
In the substrate processing apparatus according to the third aspect of the present invention, for example, the substrate manipulation means preferably manipulates the substrate by supporting the substrate only from the lower side.
According to the fourth aspect of the present invention, there is provided an anodizing system characterized by comprising any one of the above anodizing apparatuses, a conveyor robot for transferring an unprocessed substrate to the anodizing apparatus, receiving the processed substrate from the anodizing apparatus, and conveying the processed substrate to a predetermined position, and a control section for controlling anodizing by the anodizing apparatus and substrate conveyance by the conveyor robot.
According to the fifth aspect of the present invention, there is provided an anodizing system characterized by comprising any one of the above anodizing apparatuses, a conveyor robot for transferring an unprocessed substrate to the anodizing apparatus while supporting the substrate from a lower side in a substantially horizontal state, receiving the anodized substrate from the anodizing apparatus while supporting the substrate from the lower side in the substantially horizontal state, and conveying the anodized substrate to a predetermined position, and a control section for controlling anodizing by the anodizing apparatus and substrate conveyance by the conveyor robot.
According to the sixth aspect of the present invention, there is provided an anodizing system characterized by comprising any one of the above anodizing apparatuses, a washing/drying apparatus for washing and drying an anodized substrate, a conveyor robot for transferring an unprocessed substrate to the anodizing apparatus, receiving the anodized substrate from the anodizing apparatus, transferring the anodized substrate to the washing/drying apparatus, receiving the washed and dried substrate from the washing/drying apparatus, and conveying the washed and dried substrate to a predetermined position, and a control section for controlling anodizing by the anodizing apparatus, washing/drying by the washing/drying apparatus, and substrate conveyance by the conveyor robot.
According to the seventh aspect of the present invention, there is provided a processing method for a substrate, characterized by comprising the first step of substantially horizontally holding the substrate, making a negative electrode oppose an upper surface of the substrate, placing a positive electrode on a lower side of the substrate, and filling a space between the substrate and the negative electrode with an electrolyte, and the second step of applying a voltage between the negative electrode and the positive electrode to anodize the substrate while preventing a gas generated by an anodizing reaction from staying on a lower side of the negative electrode.
In the substrate processing method according to the seventh aspect of the present invention, for example, a negative electrode having a structure for preventing the gas from staying on the lower side is preferably used as the negative electrode.
In the substrate processing method according to the seventh aspect of the present invention, for example, a negative electrode having a degassing hole for preventing the gas from staying on the lower side is preferably used as the negative electrode.
According to the eighth aspect of the present invention, there is provided a processing method for a substrate, characterized by comprising the first step of anodizing the substrate using an anodizing tank, and the second step of washing the anodized substrate using the anodizing tank.
The substrate processing method according to the eighth aspect of the present invention preferably further comprises, e.g., the third step of drying the washed substrate in the anodizing tank.
According to the ninth aspect of the present invention, there is provided a method of manufacturing a substrate, characterized by comprising the steps of forming a porous layer on a surface of a substrate by any one of the above substrate processing methods, preparing a first substrate having at least a semiconductor layer on the porous layer, bonding a second substrate to a surface of the first substrate on a side of the semiconductor layer to prepare a bonded substrate stack, and separating the bonded substrate stack into two substrates at the porous layer.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings.